ABSTRACT
The lateral flow assay (LFA), also known as the immunochromatographic assay or the test strip assay, was developed in the late 1960s to find serum proteins.1 This assay format has been used in home pregnancy tests to detect human chorionic gonadotropin (hCG) in the urine specimens of pregnant women, since hCG rises rapidly and predictably in the early stage of pregnancy.2,3 With a few drops of urine sample into the round well of the cassette containing a test strip, the result can be observed based on the appearance of color bands in the observation window within 5-10 min. In 1988, the first commercial home pregnancy test was marketed by Unipath Ltd, the former owners of the Clearblue brand. This test is a urine-based single-step LFA and is simple enough to be used by untrained consumers. Until now, LFAs have been used for the qualification, semi-quantification, or quantification of target
analytes, such as pathogens,4,5 hormones,2,6 abused drugs,7,8 heavy metals,9,10 pesticides,11,12 or herbicides,13,14 for use in clinical, veterinary, agricultural, environmental, and biodefense applications.15,16 The LFA is widely used because it is portable, rapid, sensitive, and user friendly and so can be used for on-site detection, either as an over-the-counter or as a point-of-care product, by untrained operators, while providing reliable results.17
